1. Field of the Invention
This invention relates to a device and method for pneumatically tensioning a wire. More particularly, this device provides a body having a collar which abuts a structure to which the wire is to be connected in the tensioned state, and a piston having a rod which holds the wire. A pressurized gas is used to move the piston from an extended position to a retracted position within the body, which pulls the wire relative to the stationary collar, thus tensioning the wire. Adjustment of the gas pressure provides for a range of possible wire tensions.
2. Description of the Related Art
While the present invention provides for pneumatically tensioning a wire in any of a variety of situations, the device has been particularly designed for tensioning wires used in orthopedic applications, specifically for wires used for fixation of bone to external fixation devices. Wires used in conjunction with external fixation devices are commonly called "Kirschner wires" or "olive wires" and are manufactured with varying diameters.
A number of devices exist for externally fixing bone fractures and correcting bone deformities. One type of such devices, commonly referred to as the "Ilizarov System", utilizes external circular support braces. Generally, circular support braces function by extending a wire(s) through the skin, soft tissue and bone, through both sides of the body part. The extending ends of the wire are secured to a circular member at approximately the diameter of the circular member. Often, two or more circular members are combined to form a cylindrically shaped support brace, each circular member may have a wire extending across the diameter of the circular member which passes through the bone. It is desired to tension the wire to a specific tension to properly install the brace and support any related devices.
There are several known ways in which surgeons presently tension the wires. First, one method provides for a bolt with a radial hole in the shaft, commonly called a "fixation bolt". The wire is placed into the hole and the bolt is turned, thus wrapping the wire around the outer circumference of the bolt shaft to tension the wire. This method does not provide for an accurate tension load, and bending of the wire may result in premature breakage due to stress from the bending.
A number of hand-operated tensioning devices exist which may be used to tension wire or cable in orthopedic applications. Examples of such hand-operated tensioning devices are: U.S. Pat. No. 5,057,113 to Mingozzi, U.S. Pat. No. 4,966,600 to Songer, U.S. Pat. No. 4,936,843 to Sohngen, U.S. Pat. No. 4,066,082 to Arcan, and U.S. Pat. No. 4,050,464 to Hall. However, these devices suffer several disadvantages. First, these hand-operated devices are time consuming to use as they take some time to correctly position, adjust and operate. Also, these devices require the surgeon or attendant to exert a manual force upon the device to tension the wire. This could present difficulties because the surgeon's or attendant's hands may be slippery with bodily fluids or there may be insufficient room to access the device. Further, these devices do not provide for consistent tensioning loads and, hence, may lead to the brace not being properly supported on the patient.
Thus, there exists a need for a easy to operate wire tensioner device which quickly tensions the wire and provides a consistent tension on the wire.